1. Field of the Invention
The present invention relates to a highly efficient continuous process for the extraction of bromine whereby chlorine is contacted with bromide-rich brine to obtain free bromine. More particularly, the present invention is directed to a process for the extraction of bromine involving chlorine and steam distillation by vacuum operation to recover the bromine thus formed from the original brine. The brine enters a contact tower at approximately 180.degree.-210.degree. F. The contact tower is under a vacuum of about 6 to about 12 psia. Thus, when the naturally hot brine enters the vacuum contact tower, the brine is at its boiling point without the need for supplemental heating.
2. Description of the Prior Art
In the past, bromine has been produced from bromide containing solutions by the "Kubierschky's distillation method," or a modification thereof. In that method a bromide solution is fed counter-currently in a multiple plate contact tower, made of granite or similar material. Chlorine gas is fed into the bottom of the tower, and contacts the bromide solution which is fed from the top of the column. Bromine, which is produced by the reaction, is distilled from the top of the tower by the introduction of steam from the bottom of the tower, and is recovered.
Bromine recovery by this method requires a significant amount of steam for preheating the inlet brine to bring the bromine to boiling to allow the gaseous bromine produced by the oxidation reaction with the chlorine to be stripped from the solution. The amount of steam required depends upon the temperature of the brine entering the contact tower.
The prior art has utilized various processes for the recovery of bromine. Thus, U.S. Pat. No. 4,125,595 discloses a process for producing highly pure bromine from bromide-containing solutions by introducing steam and chlorine counter-current to the heated bromide-containing solution into a column having a reboiler. The reboiler has a liquid and a gaseous zone. Gaseous bromine, chlorine and steam exit the column overhead. About 40% to 80% of the theoretically needed steam is injected into the lower third of the liquid zone in the reboiler. The remainder of the steam is added depending on the amount of the bromine-chlorine steam mixture withdrawn overhead from the column into the gaseous zone of the reboiler or the lower part of the bromine column.
Another process for the recovery of bromine is disclosed in U.S. Pat. No. 4,031,194. This describes a continuous process for the preparation of bromine without loss of bromine from the bottom of the tower by removing bromine from the middle of the contact tower. The reaction between the chlorine and the brine occurs in the top of the column. A portion of the free bromine generated by the reaction is heated by the exotherm from the reaction and rises and is discharged from the middle of the contact tower. Steam distillation is used to recover the remaining bromine from the middle section.